This week Spain’s new leftwing Podemos party, which was only founded in January, overtook the two main parties (and the more traditional United Left) to become the country’s electoral frontrunner, with 27% support. In Greece the radical left Syriza is in the lead with similar polling, five points ahead of the governing New Democracy party. And in Ireland anti-austerity Sinn Féin this week topped polls in the Irish republic for the first time with 26%, following a string of mass protests against water charges.

All three parties are very different, of course. Syriza has its origins in the communist left and has been riding high for several years. Podemos erupted out of anti-austerity and privatisation protests, is strongly critical of the trade unions, and shares some of the “anti-politics” of movements such as Beppe Grillo’s in Italy. Sinn Féin is a working-class nationalist organisation that emerged from a generation of conflict to become in effect a national party of the left.

But they also have essential elements in common – which illuminate what the economic crisis is doing to politics. First, they are all operating in European countries most pulverised by austerity, and drastic cuts in output, living standards and services. Second, they largely come from outside the traditional left and labour movement – and are reacting to economic policies imposed from outside the country by the “troika” of the European commission, IMF and European Central Bank.

And crucially, they are all filling the political gap left by the social democratic and left-of-centre parties that support or are implementing austerity. While parties of the centre-right forcing through austerity are haemorrhaging votes to outfits such as Ukip, social democratic parties are punished even more severely and face potential wipeout